Control of electric motors.



No. 709,9l'5. Patented Sept. 30, I902. H. W. LEONARD.

comnol. 0F ELECTRIC moTons.

(Application filed Aug. 28. 1901.)

(No Model.)

UNITED STATES PAT NT; OFFIC HARRY WARD LEONARD, or BRONXVILLE, NEWJ YORK.

CONTROLOF ELEGTRICMOTORS,

SPECIFICAIIQN forming part of Letters Patent No. 709,915, dated September 30, 1902. Application filed August 26, 1901. Serial n5. 73,242. (No model-l I To a whom it may concern:

;. Be it known that I, HARRY WARD LEONARD,

a citizen of the United States, residing at Bronxville, in the county of Westchester and State of New York, have invented a certain new and useful Improvement in the Control;

of Electric Motors, of which the following is a specification. p

The object of my invention is to provide a rosystem for controlling the torque and speed of electric motors employed in power systems; and my invention has especial reference to the operation by electric power of cable, chain, belt,or similar conveying apparatus employed for hauling coal, freight, &,c., in such a manner that the speed and tension of the cable or similar device can be varied and in some cases reversed in direction of movement under the control of an operator.

my invention I will describe it as applied to the coaling of war-ships or other vessels at sea. r

. In carrying my inventioninto efiect I emzs-ploy two dynamo-electric machines the are matures of which are connected in a local" loop, and the armaturertermin'als of the local source are connected to the loop, so that the armatures of the dynamo-electric machines will be in multiple-arc relation to the local source. The local source is preferably a dynamo-electric machine which may be. driven by an electric motor or other form of prime mover. The fields of the-three dynamo-electric machines have windings which are separately excited. In the preferred arrange- -ment employed by me one of the dy amoelectric machines connected with the work or load operates as a generator and the other 0 operates as a motor. When my invention is applied .to the driving of a cable or similar device, I provide two drums, one for each of the first-named dynamo-electric machines.

These drums are driven in such direct-ion that as one drum pays out thecable the other drum takes it up. When employed for coaling at sea, the cable from the two drums may he carried over sheaves at the mast-head of V the collier and around one or more sheaves on the towing-vessel which is'to receive the coal, such sheaves, being suitably elevated as by means of shear-poles.

As a typicalinstance of the application of In coaling at sea it is important to preserve upon the cable oreqnivalent device which connects the collier-with the receiving vessel an approximately constant tension regardless of the relative motion of the two ships. Heretofone in attempts at coaling vessels at sea by means of cable for hauling the coal in bags a-cable extended from the collier to the receiving vessel and then back again to the collier, the bags containing the coal being attached directly to the'cable'or to a trolley moved by the cable. In these instances the cable was first moved in one direction to con- .vey the full bags of coal to the receiving-ship, and then the cable was caused to travel in the opposite direction in order to return. the empty bags to the collier. In some of these attempts three cable-lines were employed in addition to the tow-line; the upper line being what was knownas the sea-anchor line,

the other two cable-lines being the conveyin'gcable; In all cases it is important to maintain the hauling-cable at a proper tension,

and at the same time the driving apparatus must be capable of operating the cable in either 'direction and at any desired speed within limits. By means of my arrangement of driving-machines I not'only accomplish '80 this object, but the variation in tension on, the cable due to the rolling. or pitching of the vesselsis automatically compensated for bythe peculiar arrangement of thedriving-machines-that is to say, the machines are ad- '8;

,justed in the-first instance to operate at a given torque and speed. When the tension of the'cable varies, the load on the drums will vary correspondingly, resulting in a corresponding variation of the counter electromotive forces of the machines connected in the local-loop circuit, with the result thatthe' machine operating as amotor'willautomatically take a greater or lesser amount of energy, producing a correspondin g variation in torque and speed', while the machine'driven asa generator by. the moving cablewill produce a greater or lesser amount of energy, according to the speed of the cable, and thus the drums will-take up and pay out the cable '10 faster or slower, according to the variation in tension produced bythe'rolling'or pitching of the=vessels. I

In the accompanying drawings, forming a part hereof, I have illustrated the applical tion'of my invention to the coaling of ships at sea.

Figure l is a conventional illustration ot'a ship towing a collier and having a battlingcable extending from sheaves at the forward masthead of the collier to a suitable sheave on shear-poles erected on the towing vessel. Fig. 2 is a diagram illustrating the arrangement of the main and local sources of energy, the driving machines, cable-drums, &;c., and the circuit connections. Fig. Sshows a modification of the local closed loop in which the armatures ot' the driving dynamo-electric machines are connected.

Referring to Fig. 2 of the drawings, A isa source of practically constant electromotive force-snch forexample, as a dynamo-electric machinefro|n which extends the circuit 1 2 for supplying current to lamps, motors, or other'translating devices. Bis a dynamoelectric machine driven as a generator by electric motor 0 or by any other form of prime mover, such as a steam-engine or gas-engine. The field of dynamo B is partially or wholly separately excited, and, as shown in the diagram, the fieldwinding is connected across the circuit 1 2, preferably through reversingrheostat R. D and E are dynamo-electric machines geared or otherwise connected to cable-drums D and E, respectively, one of said machines operating as a motor and the other as a generator-2'. 6., the armature geared to the take-up drum acts as a motorarmature and the other acts as a generatorarmature. The field-windings of machines D and E are connected in multiple-arc relation across circuit 1 2 through reversingrheostats R and B, respectively, although in some instances they may have additional windings and in many instances the reversing-rheostats R and B may be omitted.

The armatures of machines D'and E are connected in a closed loop (indicated by the circuit connections 3 4 5 6) and which loop is connected across thearmature-terminals 7 8 of machine B, sothat the armatures of machines D and E will be in multiple-arc relation across circuit 7 8. It the fields of machines D and E are continually excited and machine B is continually driven, it will be evident that an operator by manipulating the field reversing-rheostat R can produce at the armature-terminals of machines D and E any desired electromotive force within limits and that the electromotive force can be varied and reversed at will. It will also be evident that by properly exciting the fields of machines I) and E the speed of the two armatu res can be made equal at all times and that therefore the cable can be paid out from drum E at the same speed that itis taken up by the drum D, or vice versa. It will also be evident that it the field ofoue machine is slightly weakened the counter electromotive force of that machine will be reduced below that of the other machine if the speed of the two armatures are held relatively the same by the cable connecting them. Let it be supposed that machine D is driving drum D, so as to take up the cable, the field of that machine being weakened. That machine will tend to run faster in its weakened field and in so doingmust drive E faster, thus raising its electromotive force and making it a generator. The result will be that a current will circulate in the local loop 3 4 5 6, this local current being due to the difference in the electromotive forces of the machines D and E. In order to simplify the study of the results, let it be supposed that the distance between the receiving vessel and the collier or, in other words, between-the drums D and E- and sheave G on the shear-poles H is constant and that machine D is operating as a motor driving drum D, so as to take up the cable. The pull thusgiven to the cable will tend to drive machine E through the unwinding, of the cable from drum E. Disregarding all losses due to friction and heat in the electrical apparatus, it will be evident that the fields of machines D and E can be so adjusted that machine E will be driven at such a speed by the cable that its electromotive force will be exactly equal to the electromotive force supplied by machine B. In that case there will be no current in path 3 6 and current will flow from machine 13 through path 74 5 S. If now the field of D is further weakened, the armature of machine'D will tend to speed up, and in so doing must drive drum E and armature of machine E faster, causing machine E to operate as a generator, which will cause a current to flow in the local loop 3 4 5 6. Machine B will continue to supply another current in the circuit 7 4 5 8 and the two currents will be joined in parallel in the armature of machine D. As above stated, the current in the local loop will be due to the difierenco between the electromotive forces of machines D and E, and this current can be controlled by the manipulation of rhcostats R and R If desired, these rheostats. may be varied inversely. The current in the local loop will produce a tension upon the cable, and since the current in this loop can be controlled the tension of the cable can likewise be controlled. The speed of the cable can be controlled by controlling the electromotive forceof machine B or by simultaneously and similarly varying the fields of machines D and E. To reverse the direction of motion of the cable, the electromotive force of machine B may be reversed by the reversing field-rheostat R or by reducing the electromotive force of that machine Ioc IIC

practically to zero and then simultaneously reversing the armature connections of machines D and E, or the field connections of those machines may bereversed. If while the cable is in operation with a certain tension upon it the vessels should lurch toward each other, so that the distance between them and the tension of the cable is suddenly reduced, machine D under those conditions will immediately increase its speed and take upapparatus.

. I machines,-the resistance and contacts will be handle, and when it is desired to vary the 1 compensate for "variations in tension or load.

'If desired, I may wind thefield-coils of either will insert the resistance in the local loop 3 I located in close proximity, so as to be within stated the contact-arms may be connected by ratus, it' will be evident that the controllers may be located on the other vessel and con- -It will also be understood that my-inventio may be applied to the hauling ofcable con theislack in the cable. If the distance between the vessels were to suddenly increase due to rolling or pitching, the current in the local loop will instantly increase due to the increased speed of the cable. Thus it will be seen that the slackin the cablewill be auto-' matically. maintained practically uniform.

or bothmachines E and D so that they will havesome series turns which are normally accumulativdto the separately-excited turns, as this makes them act with flexibility over a wider range'at any speed, as will be understood by those skilled in the art.

To protect machines D and E against an excessive current, I may connect an automatic circuit-breaker in the local loopfor example, in the circuit 3 6, as shown in Fig. 3. In that illustration I represents an automatic overload circuit-breakershnnted by a resistance J. If the current in the local loop becomes excessive, the switch will automatically open and In practice rheostats R, R, and R will be reach of one operator, and these rheostats are preferahlylocated near machines D and E, so that-the operator will be imposition to observe and control the operation of the entire Whenit is desired to shift the rheostats R and R uniformly to control those arranged in juxtaposition, so that thetwo contact arms may be moved'by one operating fields inversely the field-coil connections,with the resistances, will be made so that as resistance is inserted in the field of one ma-' chine resistance will be cut out of the field of the other machine. v

Instead of arranging the rheostatsas above.

suitable gearing so as to move uniformly and with the same or opposite elfect, or the contact-arms may be geared so as to moveat different speeds according to the conditions of operation. While the.controlling-rheostats are-preferably located on the vessel provided with the machines fordriving the conveying-appanected therewith by an electrical conductingcable. It will also be evident tha't'a =set of controllers maybe proy ided on each vessel.

-Veyers on land 'or for driving any other can veyer system or for driving any form-of vehicle Qr/apparatus wherein it is essential to I do not claim herein the method of "controlling electric-power apparatus involved in the operation of the conveyer system above described, since that feature of my inyention forms the subject-matter of a divisional ap- I plication, filed December 10, 1901, Serial No. 85,360.

What I claim is r 1. Ina conveyer system, the combination with the conveying apparatus, of two dynamoelectric machines for operating said apparatus, one of said machines operating as a motor to drive the apparatus, and the other machine operating as a generator driven by said apparatus.

2. In a conveying system, the combination with the conveying apparatus, of two dynamoelectric machines for operating said apparatus, and a main source of electric energy to which said machines are connected, one of said machines operating as a motor through energy received from said source to drive the apparatus, and the other machine operating as a generator driven by said apparatus and supplying energy to the motor. I

3. In a conveyer system, the combination 'wi th the conveying apparatus, of twodynamoelectric machines for operating said appara-' ratus, said machines being connected in series in a closed loop, and a main source to which said loopis connected, one of said machines operating-asa motor to drive the apparatus, and the other machine operating as a generator drivenby said apparatus, and said motor receiving-energy'from the source and said generator. 1

4. 'In a conveyer system, the combination with the conveying apparatus, of two dynamoelectric machines for operating said apparatus, one of said machines operating as a mo-' tor to drive the apparatus, and the other machine operating as a generator driven by said apparatus, and means for controlling the direction pf movement of said conveying apparatus.

5. In a conveyer system, the combination with the conveying apparatus, of two dynamo- 'electrie machines vfor operating said apparaoperating as a generator driven by said appa ,ratus, and means for controlling the speed of rotation of said machines. p

7. In a conveyer system, the combination with the con veying apparatus, of two dynamo electric machines for operating said apparatus, oneofsaid machines operating as a motor to drive the apparatus, and the other machine operating as a generator driven by said apparatus, and means for simultaneously controlling the speed and direction of rotation of said machines. 8. The combination with a source of elecenergy received from said source, and two dynamo electric machines D and E having their field-windings connected with said source, and their armatures connected in multiple-arc relation across the armature-terminals of machine B, the latter machine and one of said machines D and E generating electric energy and the other machine absorbing electric energy.

10. The combination with a main source of electric energy, of a dynamo-electric machine B, having its field-winding connected with said main source and its armature driven by energy received from said source, and two dynamo-electric machines D and E having their field-windings separately excited from-said source, and theirarmatures connected in multiple-arc relation across the armature-terminals of machine B, the latter machine and one of said machines D and E generating electric energy and the other machine absorbing electric energy.

1].. The combination of a source of electromotive force, two dynamo-electric machines whose armatures are in multiple arc across said source, means for varying the electrometive force of said source to vary the speed of the said armatures, the field-windings of said dynamo-electric machines being connected across an independent electromotive force, and means for inductively varying the relative speeds of the two armatures. 12. The combination of a dynamo-electric machine having a separately-excited fieldwinding and two other dynamo-electric machines whose armat-ures are connected in multiple-arc relation across the armatureterminals of the first-named dynamo, and both of said machines having separately-excited field-windings.

13. The combination of a local circuit, two

. dynamo-electricmachines whose armatures are connected in said circuit, a cable or equivalent device mechanically connecting the two armatures and means whereby the current in the local circuit can be varied for the purpose of varying thetension of the cable.

14. The combination of a local circuit, two dynamo-electric machines whose armatures are connected in said circuit, a cable or equivalent device mechanically connecting the two armatures, and means for varying the eleotromotive forces supplied to the two ar- 17. In a conveyer system connected 'be-" tween moving objects, the combination of a conveying-cable or equivalent device, an electric motor for driving said cable, and electrical means for varying or controlling the sgeedf said cable.

. n a conveyer system connected betw en moving objects, the combination of a conveying-cable or equivalent device, an electric motor for driving said cable, and electrical means for varying or controlling the direction of movement of said cable.

19. The combination of two dynamo-electric machines whose armatures are electrically connected together, a cable or equivalent device mechanically connecting the two armatures and electric means whereby the tension of the cable can be varied at the will of the operator.

'20. The combination of two dynamo-electric machines whose armatures are electrically connected together, a cable or equivalent device mechanically connecting the two armatures, and means whereby the relative speeds of the two armatures can be varied at the will of the operator;

2].. The combination of two dynamo-electric machines whose armatures are electrically connected together, each armature being geared to a drum, a cable mechanically connecting the .two drums, and means for controlling the speed of at least one of the dynamo-electric machines.

22. In an apparatus for coaling at sea, the

combination of a moving cable and electricmeans for controlling the tension of the cable by the generation of electric energy.

- 23. In an apparatus for conveying materials to or from a vessel which is free to move upon the water, the combination ofacable connecting the vessel with another object above the surface of the intervening water, and electric means for controlling the tension of said cables so as to maintain the cable clear of the water under conditions of relative movement of the vessel and the other object. 24. In an apparatus for conveying material to or from a vessel which is free to move upon the surface of the water, the combination of a.

cable, chain, or equivalent device connecting the vessel with another object, a dynamo-electric machine whose armature is mechanically connected with said cable, chain, or equivaq lent device, and means for controlling the currentin-said armature whereby the tension of said cable can be controlled.

25. In an apparatus for conveying materials to or from a vessel which is free to move upon the surface of the water, the combination of a cable, chain, or equivalent device connecting the vessel with another object, a dynamo-electric. machine whose armature is mechanically connected with said cable, chain, or equiva lent device, and electric means for keeping the tension upon the cable sufiiciently constant to keep the cable clear of the Water when the distance between the vessel and the other object is reduced.

26. In an apparatus for conveying, materials to or from a vessel which is free to move'upon the surface of the water, the combination of a cable, chain, or equivalent device connecting the vessel with another object, a dynamo-electric machine whose armature is mechanically connected with said cable, chain, or equivalent device, and means for controlling the tension upon said cable when there is a movement of the vessel relative to the other object, by controlling the torque of the armature of said dynamo-electric machine.

27. In an apparatus for conveying materials to or from a vessel which is free to move upon the surface of the water, the combination of a cable, chain or equivalent device connecting the vessel with another object, a dynamo-electric machine whose armature is mechanically connected with said cable, chain or equivalent device, and means for controlling the tension upon said cable when there isamovement of the vessel relative to the other object by controlling the current in one of the elements of said dynamo-electric machine.

This specification signed and witnessed this 23d day of August, 1901. i

H. WARD LEONARD.

, \Vitnesses:

JOHN LEONARD KEBLER, HARRY F. DAVIDSON. 

